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A massive manhunt is on for two California fugitives who cut jail bars and rappelled out of their second-story cell window in the oldest section of the Santa Clara County Main Jail on Thanksgiving eve, officials said early Thursday morning.

Santa Clara County Sheriff’s spokesperson Sgt. Rich Glennon said there were four inmates who cut the bars in their cell window in the oldest part of the main jail around 11 p.m. Wednesday and escaped with the help of bed sheets and clothing. A deputy on patrol noticed the clothing hanging from the window and two of the inmates were immediately caught. But two others got away. It is unclear how the inmates got their hands on tools to cut the window bars, Glennon said.

Glennon said it's not clear whether the inmates were armed, but they should be considered “dangerous and desperate.” San Jose police has increased patrolling in nearby neighborhoods, and has stepped up patrol for San Jose’s annual Turkey Trot race, expected to start at 8:30 a.m. About 200 police officers are taking part in the annual Silicon Valley event.

The Santa Clara County Sheriff’s office tweeted out photos of the escaped inmates at 3:04 a.m., asking the public to call 911 if they were spotted. The sheriff’s office is using its helicopter as well as multiple K-9 units from a number of law enforcement agencies to track the escapees.

“The main thing is we’re asking for the public’s assistance – there’s an active search going on,” Glennon said. “There has never been an escape from Main Jail South in this kind of fashion. Anyone willing to escape from jail is desperate, don’t try to apprehend them, but notify law enforcement if you see them.”

The incident wasn’t caught on camera because there are no cameras in the part of the jail where the inmates were living. Sheriff’s deputies said this particular section is older, and was constructed in the 1950s.

Sources from inside the jail told NBC Bay Area it’s possible the inmates had help in getting away.

Santa Clara Sheriff's office said the first inmate who escaped is 33-year-old Rogelio Chavez, who stands about six feet tall, weighs 190 pounds and has the letter B tattooed on the left side of his neck. He also has a line drawn through his left eye. Glennon said he was being held since Aug. 17 on various charges including burglary, extortion, false imprisonment, resisting arrest, and firearms violations.

The second escapee is 26-year-old Lanon Desean Campbell. He is about six feet four inches tall and weighs 210 pounds. Campbell was being held since February 2015 on various charges including robbery, false imprisonment, criminal threats and firearms violations, records indicate.